looks like ronix uses FCS fin boxes. you can use just about any FCS fins. I am have a set of H-2 large fins shipped up to try out on one of my triple x boards. i will let you know how they feel. I have loved the PC-7 setup as well but wanted something with less rake to the fin to loosen it up.
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Depends on what year your board is. They now have FCS fins, my 2010 does not. It has traditional wakeboard fins. I have 1.75, 2.75, and 3.5's. I'm always changing them. I usually like his one center fin. I believe they changed to the FCS fins in 2011